After rough sawn boards are produced in a sawmill, they are commonly run through a plurality of planing, grading, trimming, cutting, and sorting operations. In current cutting, trimming, sorting operations, a plurality of boards of various lengths, up to 20 ft. long, for example, are fed by a conveyor along a predetermined path in a machine direction. The boards are oriented orthogonally to the machine direction. The conveyor has lugs that advance the board through a sensing station. At the sensing station, shape properties of the board are determined, including length, width, wane (missing wood due to circular shape of the tree), crook and bow. These shape parameters are evaluated along the length of each board to determine the grade of various portions of the board. The board advances in front of a human operator who will make visual based grade decisions based on quality parameters that cannot be determined by the sensing station. The information from the sensing station and the human operator are sent to a programmable logic controller, where the data is analyzed to determine the optimal grade and length solution for the individual board. The programmable logic controller controls a plurality of saws that are spaced laterally across the conveyor at a sawing station. Depending upon the length and grade information, the board can either pass under the saws without being cut, or it can be cut at a predetermined location along the length of the board, depending upon the information received by the programmable logic controller from the sensing station and from the human operator.
After boards pass the sawing station, the boards pass over a plurality of aligning rollers. These rollers are oriented parallel to the machine direction and rotated in a clockwise direction looking in the machine direction. As the boards pass over these rollers, they are moved to the right looking in the machine direction, until their ends abut a rail running parallel to the right-hand side of the conveyor, normally referred to as a lumber line. If a board has been split in two segments, the programmable logic controller will leave an extra space on the conveyor so that the second segments of the board, which occupied one space on the conveyor when being cut, is now indexed so that it occupies a successive location on the conveyor. The second segments of the cut boards are also aligned against the right-hand lumber line.
Downstream from the aligning rollers lie a plurality of receiving bins. The receiving bins are positioned under the conveyor in a conventional manner. The programmable logic controller operates drop gates on the conveyor so that boards of common length and grade are dropped into predetermined bins. In this manner, a single bin receives boards of a single length and grade. The bins are periodically emptied and the boards subsequently stacked for shipment in a conventional manner.
Because each of the boards, whether a single uncut board or a board that has been cut in two, occupy one station on the conveyor downstream of the saws, the actual throughput of the cutter trimmer is reduced by the number of boards that are cut in two because the second segment must also be indexed against the right-hand lumber line. For example, if 10% of the boards are cut in two, then the actual throughput from the machine is reduced by 10%, relative to the number of boards that can be fed into the machine. It is therefore desirable to provide a method and apparatus for increasing the efficiency of the cutter-sorter of the type just described.